Double diaphragm pumps alternately pressurize and exhaust two opposing motive fluid chambers to deliver pumped media during each stroke of the pump. Pressurizing the motive fluid chambers often results in operating efficiency losses as some of the motive fluid communicated to the chambers during each stroke does not contribute to the pumping action. In an attempt to mitigate this shortcoming, some prior pumps have interrupted the supply of motive fluid using devices having electrical components. Such pumps, however, may have limited utility in industrial applications where the use of electrical components necessitates safety measures that are not typically required for purely mechanical devices.